Corrosion of metal surfaces in an aqueous medium has long been a problem for the oil and gas industry. It is well known that during the production of oil and gas several other corrosive components are present such as brines, organic acids, carbon dioxide, hydrogen sulfide, and microorganisms. These aggressive constituents can cause severe corrosion to metal pipes, which are often made of low-alloy steels. This problem is even more troublesome in deep-sea operations where replacement of corroded equipment is difficult and costly. Therefore, it is common practice to employ corrosion inhibitors during the production, transportation, storage, and separation of crude oil and natural gas.
Corrosion inhibitors are usually surface-active compounds that form protective coatings on the surface of metal components, which come in contact with corrosive environments, and thus suppress corrosion. Common corrosion inhibitors are composed of amines, condensation products of fatty acids with polyamines, e.g. imidazolines, or quaternary ammonium compounds. Among the most frequently used corrosion inhibitors in crude oil and natural gas extraction are imidazoline derivatives. Alternative corrosion inhibitors that can be used alone or in combination with known corrosion inhibitors are being sought by the industry.